Flat panel speaker assembly

ABSTRACT

A speaker assembly which includes a first diaphragm, a second diaphragm and a driver operationally positioned in an enclosure formed by the first diaphragm and the second diaphragm. The second diaphragm is made of a material composition which allows it to block sound energy, and reflect sound energy along to the first diaphragm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to speakers, and more particularly, but notexclusively, to flat panel speakers used in public address systems.

2. Background

Audio speakers come in different configurations. Generally, an audiospeaker is a device which takes an electrical signal and translates itinto physical vibrations, which create sound energy.

A typical speaker configuration uses a driver or exciter that producessound energy by rapidly pushing and pulling in a piston-like action, alight weight diaphragm, typically fashioned into a “cone” shape. Thecone shaped diaphragm is usually made of paper, plastic or metal, and isattached to a suspension module. The cone shaped geometry is used tocreate a rigid mechanical structure that can be kept light weight. Thecone shape provides rigidity, which is important to ensure that thediaphragm can be effectively driven by the driver.

The suspension module is a rim of flexible material or a speciallycontoured shape of the same cone material that allows the cone to move.The suspension module is attached to the driver's metal frame, calledthe basket, and controls the cone diaphragm's maximum amplitude.

The narrow end of the cone is connected to a voice coil. The voice coilis attached to the basket by a suspension spring of the voice coil, alsoknown as a spider. The spider holds the coil in position within amagnetic gap, but allows the coil to move freely back and forth.

Unfortunately, the cone type speaker assembly can be hard to install inan aircraft interior, since the loudspeaker assembly height can be high,such as between 2 to 3 inches. The speaker assembly may also be heavyand require a speaker grill. In addition, a cone diaphragm speaker hasnarrow angle sound projection and is therefore, directional, which doesnot provide adequate coverage in an aircraft interior.

For public address (PA) speaker applications, flat panel speakers havemany advantages over cone type speakers. For example, flat panelspeakers provide dispersion of over 120 de- grees versus a cone speaker,which has a dispersion of about 80 degrees. The flat panel speaker alsohas no on-axis beaming problem and can be made to blend into specificarchitecture and thus be virtually “invisible”.

However, when efficiency is a concern (for example, in an airplane PAapplication it is desirable to that the speaker have low powerconsumption to minimize the impact keep on emergency battery packageweight), the typical flat panel speaker is less efficient thanconventional cone speakers due to the difference of the “moving mass”between the two speaker designs.

Conventional cone speakers have the strength advantage provided by thegeometry of the light weight paper cone diaphragm. Flat panel speakershave a flat diaphragm, which provides no specific geometrical advantageto help strengthen the diaphragm. The soft flat diaphragm creates selfcanceling, which does not provide good and effective audio performance.To reinforce the flat diaphragm structure, more solid and thickermaterials must be used, such as a sandwich lay-up (i.e. honey comb,foam, flute structure, or even solid acrylic board etc). However, theseflat diaphragm reinforcing materials add 20 to 100 times the weightrelative to paper cone speakers, which lowers the speaker's efficiency.

Unfortunately, it has been shown that even using the lightest availableflat panel diaphragm materials available, such as polyester foam board,the flat speaker diaphragm is still at least 10 times heavier thanconventional cone speaker diaphragms, which causes a 6 to 12 dB decreaseaudio level performance than the highest efficiency cone speaker. Inaddition, the flat panel speakers have poor high frequency response,which starts to roll off as early as from 800 Hz, due to aninappropriate material flexibility coefficient.

Therefore, there is a need for a speaker assembly, which overcomes therestrictive nature of cone type speaker assemblies and theinefficiencies associated with conventional flat panel speakers,provides optimum sound quality, is cost effective and is easy toinstall/maintain.

SUMMARY OF THE INVENTION

The present invention provides an isobaric flat panel speaker assemblywhich solves the inefficiencies of conventional flat panel speakers.

In the present invention, the flat panel speaker assembly capturesotherwise unused audio energy, which generally escapes from the backside of conventional flat panel speaker configurations. The presentinvention converts the escaping audio energy to right phase and tunes itto a preferred frequency range. For example, in a PA application in anaircraft interior, the mid frequency range of between 300 Hz and 1 KHzis desired. The escaping audio energy is tuned to this audio frequencyrange and then redirected towards the front side of the speakerproviding a higher output performance.

In one aspect of the invention a speaker assembly is provided whichincludes a first diaphragm, a second diaphragm, and a driveroperationally positioned in an enclosure formed by the first diaphragmand the second diaphragm. The second diaphragm is made of a materialcomposition which allows it to block sound energy, and reflect soundenergy back to the first diaphragm.

In another aspect of the invention, an aircraft is provided whichincludes an audio system. The audio system includes an input device, anamplifier; and a speaker assembly. The speaker assembly includes a firstdiaphragm and a second diaphragm, where the second diaphragm has amaterial composition which allows it to block sound energy and reflectsound energy to said first diaphragm.

In tests, an isobaric flat panel speaker assembly of the presentinvention was shown to boost the audio output performance by about 4 to8 dB. With this boost in audio output, the flat panel speaker of thepresent invention is capable of the same average level of performanceefficiency as high efficiency cone speakers.

The flat panel speaker assembly of the present invention can be pluggedinto a mating panel structure formed into an aircraft bulkhead duringthe bulkhead assembly process. Once the aircraft interior is completed,there is no visual impact on the appearance of the interior bulkheads.Moreover, because of the modular nature of the speaker assembly, repairand maintenance of the flat panel speaker can be accomplished withminimal impact to the aircraft bulkhead.

Additional advantages, objects, and features of the invention will beset forth in part in the detailed description which follows. It is to beunderstood that both the foregoing general description and the followingdetailed description are merely exemplary of the invention, and areintended to provide an overview or framework for understanding thenature and character of the invention as it is claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide further understandingof the invention, illustrate various embodiments of the invention, andtogether with the description serve to explain the principles andoperation of the invention. In the drawings, the same components havethe same reference numerals. The illustrated embodiment is intended toillustrate, but not to limit the invention. The drawings include thefollowing Figures:

FIG. 1 is a block diagram of a PA system in accordance with anembodiment of the present invention;

FIG. 2 is a simplified cross-sectional view of the flat panel speakerassembly in accordance with an embodiment of the present invention

FIG. 3 is a perspective view of a mounted flat panel speaker assemblyrepresentative of test models used in accordance with embodiments of thepresent invention;

FIG. 4 is a block diagram of an aircraft using the speaker configurationin accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

To facilitate an understanding of the present invention, the generalarchitecture and operation of an audio system (for example, a PA system)will be described. The specific architecture and operation of thepresent invention will then be described with reference to the generalarchitecture.

FIG. 1 shows a block diagram of a typical PA system 10 used in anaircraft, according to one aspect of the present invention. PA system 10includes a microphone or similar audio input device 20 that is capableof receiving an audio input and converting it into an electrical signal,and an amplifier 30, which is used to amplify the electrical signals. PAsystem 10 uses a speaker assembly, such as flat panel speaker assembly40 of the present invention to convert the amplified electrical signalsinto sound waves.

It is noteworthy that although FIG. 1 is used to show an example of atypical PA system, the adaptive aspects of the present invention are notlimited to a PA system. The speaker configuration/design/structuredescribed below may be used with any audio system.

FIG. 2 is a simplified cross-sectional view of a flat panel speakerassembly 100 (hereinafter “speaker assembly 100 ”) in accordance with anembodiment of the present invention. Speaker assembly 100 includes maindiaphragm 102, secondary diaphragm 104, and driver 106. A wall structurecouples main diaphragm 102 and secondary diaphragm 104 together forminga shallow enclosure 108, defining a gap 110 formed between the twodiaphragms, in which driver 106 is positioned. Diaphragms 102 and 104can be formed in any suitable shaped, such as round or rectangularshapes, and can be large or small depending on the application.

Driver 106 is safely secured and strategically positioned in speakerassembly 100 to assure secure coupling conditions between driver 106 andmain diaphragm 102, and to ensure optimum performance conditions.Structure 106A supports and/or locates the driver assembly 106 in theproper position. In accordance with an embodiment of the presentinvention, secondary diaphragm 104 is free from physical contact withdriver 106. Driver 106 is offset from second diaphragm 104 by gap 110.In one embodiment, the distance between diaphragms 102 and 104, and thusthe height of speaker assembly 100, is about 1 to 2 inches.

Speaker assembly 100 can be installed, for example, by inserting theentire speaker assembly 100 into a pre-cut hole on a ceiling panel 112during a lay up process (i.e. during bulkhead fabrication). Speakerassembly 100 may be glued or similarly mounted into panel 112 usingconventional speaker mounting means. A covering 114, such as a laminatecovering, may be used to cover speaker assembly 100, making speakerassembly 100 virtually invisible to the interior of the aircraft.

In one embodiment, main diaphragm 102 and laminate covering 114 aredesigned to operate together in audio terms to produce any desired PAquality performance. In this embodiment, the weight, stiffness, rigidityand thickness of laminate covering 114 may be modified to provideoptimum sound quality. For example, the thickness of the laminatecovering may be determined by a progressive thinning process where thethickness is decreased and each thinning step is followed by an audiotest to verify optimum sound quality results. It is noteworthy that thepresent invention is not limited to any particular material orthickness. The thickness depends on the density of laminate covering 114and also on the overall diameter of speaker assembly 100.

In operation, a typical flat panel speaker emits audio energy equally onboth sides of its respective flat diaphragm. In accordance with anembodiment of the present invention, speaker assembly 100 operates toredirect the “rear directed” or “back firing” audio energy to benefitthe “front directed” or “front firing” audio energy, thus, increasingthe overall dB level output of speaker assembly 100.

Speaker assembly 100 is not a coherent speaker that works by pumping airin and out in a coherent manner, thus, the function of redirecting audioenergy is not accomplished by phase tuning or speaker cabin air pressuremodification (unlike a cone speaker assembly). Rather, the redirectionof the audio energy is accomplished by means of resonant and reflectiontuning, controlled primarily by the function of secondary diaphragm 104,and its distance from main diaphragm 102. Details of the redirection ofaudio energy in accordance with the present invention are describedbelow.

As described above, speaker assembly 100 has dual diaphragms—main oractive diaphragm 102 and secondary or passive diaphragm 104. Unlike someconsumer sub-woofers that use a passive radiator to utilize wooferenergy more effectively, passive diaphragm 104 of speaker assembly 100is not intended to emit or radiate sound outward (i.e. to the rear ofthe speaker).

Referring again to FIG. 2, secondary diaphragm 104, although referred toas a diaphragm, can be described as a functioning baffle of enclosure108. The significance of this description, is that generally, speakerbaffles are made of a rigid material that can block sound energy fromradiating out of the speaker enclosure. Thus, in accordance with anembodiment of the present invention, passive diaphragm 104 is a stifferdiaphragm than the soft or flexible active diaphragm 102.

For ease of understanding, below is a detailed description of aparticular embodiment of the present invention, which is not intended tolimit the invention in any manner.

Accordingly in this exemplary embodiment, speaker assembly 100 caninclude active diaphragm 102, which is made of one ply of 120 glass andone ply of glass fly Screen on separate sides of a Nomax honeycomb corehaving a thickness of about 0.12 inches. The size and materialcomposition of active diaphragm 102 in this embodiment is a result of atimely research and testing—matching (installed) with the audioattributes of a 0.375 (⅜″) thick ceiling laminate 114.

In this embodiment, the use of active diaphragm 102 alone performs inaudio quality tests at about 8 dB less efficiency than productionairplane PA speakers. Using diaphragm 102 provides higher efficiency anddynamic performance than conventional flat panel speakers.

In accordance with the present invention, the addition of passivediaphragm 104 to speaker assembly 100 increases the output efficiency.It is noteworthy that the composition of passive diaphragm 104 issignificant to the successful implementation of the present invention.Improper material uses may actually reduce the efficiency of activediaphragm 102.

In this embodiment, passive diaphragm 104 can be made of one ply of 120glass and one ply of 181 glass on separate sides of a Nomax honeycombcore. Lab tests have verified that the combination of dissimilarcomposition diaphragms 102 and 104 boosted the audio output by anadditional 4-8 dB of speaker output at a range of about 500 Hz to 11kHz.

In this embodiment, passive diaphragm 104 is about 30% to 75% stifferthan active diaphragm 102. Being stiffer, the mass of diaphragm 104 isnot necessary so much heavier than active diaphragm 102. In one aspect,the mass is about 10% heavier.

Given the structure described in FIG. 2, in operation, sealed enclosure108 traps most back firing audio energy. The back firing audio energyfrom active diaphragm 102 activates passive diaphragm 104 to vibrate.However, since passive diaphragm 104 is a stiffer diaphragm, it blockssound energy rather than radiates sound energy.

In addition to blocking sound energy, passive diaphragm 104 reflectssound energy back to active diaphragm 102. At the same time, thematerial composition of passive diaphragm 104 creates a range of desiredresonance in reaction to the performing audio frequencies and level. Theresonance, along with the reflection of sound energy, and the tailoreddistance between both diaphragms 102 and 104, can assure additionalfrequency output of between about 500 Hz -11 kHz of speaker assembly100.

Test data confirms the significant improvement of the dB output ofspeaker assembly 100. FIG. 3 is a perspective view of a mounted flatpanel speaker assembly 100 representative of a test model incorporatingthe embodiment of the present invention described in FIG. 2.

Table 1 summarizes the results of an on-axis test performed using thisembodiment of speaker assembly 100. On-axis measurements were made atvarying frequencies of a speaker assembly having active diaphragm 102only and a speaker assembly 100 having an active diaphragm 102 and apassive diaphragm 104 positioned in enclosure 108 with a predeterminedgap 104 in accordance with an embodiment of the present invention. TABLE1 Frequency 125 250 500 1000 2000 4000 with passive 54.6 65.8 76 80.477.9 74.5 diaphragm without 54.8 67.7 72.6 76 77.7 74 passive diaphragm

The on-axis data in Table 1 shows an increase, for example, of 4.4 dB at1 kHz with passive diaphragm 104.

Some test were conducted which compared speaker assembly 100 with atypical cone speaker, at 60 degrees off-axis at a two meter distance.Speaker assembly 100 measured more dB output than the cone speaker dueto the weak dispersion nature (less than 90 degrees) of cone speakers,and the wider dispersion (over 120 degrees) capability of speakerassembly 100. The wider angle coverage capability of speaker assembly100 is particularly beneficial for covering seats in the interior of anaircraft that are located away from the center aisle (i.e. windowseats). Conventional cone speaker would have to be driven much louder inorder to cover wider area, at a cost of greater amplifier power, and maybecome unbearable for passengers sitting along the axis of the speaker.

FIG. 4 shows a block diagram of an aircraft 400 having PA system 10incorporated therein. In this embodiment, aircraft 400 includes pluralspeaker assemblies 100 (shown as Speaker A, Speaker B. . . Speaker N).The plurality of speaker assemblies 100 receive an electrical signalfrom amplifier 30 that receives an input from microphone 20 and produceoptimum sound within at least a frequency range of 300 Hz to 5,000 Hzwith efficiency of 1 watt (root mean square (“RMS”) to produce anaverage of 80-95 dB audio level. In another embodiment, speakerassemblies can be adapted to further produce acceptable audio in afrequency range that is both lower than 300 Hz and/or higher than 5,000Hz. However, low frequency extension range may have to be controlled(trim or limited) to avoid possible airplane interior architectureresonance. It is noteworthy that the system in aircraft 400 may be usedin plural applications, where flat panel speakers can be used.

As will by now be evident to persons of ordinary skill in the art, manymodifications, substitutions and variations can be made in and to thematerials used for the reliable, low-cost, speaker assembly 100 of thepresent invention without departing from its spirit and scope. It isunderstood, that the speaker system of the present invention may finduse in vehicles or general domestic and commercial applications otherthan airplanes. All such uses are within the scope of the presentinvention.

Accordingly, the scope of the present invention should not be limited tothe particular embodiments illustrated and described herein, as they aremerely exemplary in nature, but rather, should be fully commensuratewith that of the claims appended hereafter and their functionalequivalents. What is claimed is:

1. A speaker assembly comprising: a first diaphragm; a second diaphragm;and a driver operationally positioned in an enclosure formed by saidfirst diaphragms and said second diaphragms, said second diaphragmhaving a material composition causing it to block sound energy andreflect sound energy to said first diaphragm.
 2. The speaker assembly ofclaim 1, wherein said first diaphragm is an active diaphragm configuredto radiate sound energy.
 3. The speaker assembly of claim 1, whereinsaid first diaphragm comprises a material composition including one plyof 120 glass and one ply of glass Fly Screen layered on separate sidesof a Nomax honeycomb core.
 4. The speaker assembly of claim 1, whereinsaid first diaphragm comprises a thickness of about 0.12 inches.
 5. Thespeaker assembly of claim 1, wherein said second diaphragm comprises amaterial composition including one ply of 120 glass and one ply of 181glass layered on separate sides of a Nomax honeycomb core.
 6. Thespeaker assembly of claim 1, wherein said second diaphragm comprises athickness of about 0.12 inches.
 7. The speaker assembly of claim 1,wherein the speaker assembly is installed for use with an audio system.8. The speaker assembly of claim 1, wherein the speaker assembly isinstalled for use with a public addressing system of an aircraft.
 9. Thespeaker assembly of claim 1, wherein the second diaphragm is free fromcontact with said driver.
 10. The speaker assembly of claim 1, whereinsaid enclosure defines a gap between said first diaphragm and saidsecond diaphragm.
 11. The speaker assembly of claim 10, wherein said gapcomprises a dimension of between about 1 and 2 inches.
 12. The speakerassembly of claim 1, wherein the first diaphragm and the seconddiaphragm are operationally configured to produce sound energymaintained in a frequency range of about 300 Hz to about 5,000 Hz whensubject to an appropriate input signal.
 13. The speaker assembly ofclaim 1, further comprising a cover configured to function operationallywith the first diaphragm when subject to an input signal.
 14. A speakerassembly comprising: a first diaphragm having a first materialcomposition; and a second diaphragm having a second material compositionconfigured to form an enclosure with said first diaphragm, which definesa gap therebetween; said second diaphragm having a material compositioncausing it to block sound energy, and reflect said sound energy to saidfirst diaphragm causing said first diaphragm to produce sound energy ina frequency range of about 300 Hz to about 1,000 Hz of between about a80 and 95 dB audio level when subject to an appropriate input signal.15. The speaker assembly of claim 14, further comprising a driveroperationally positioned in said enclosure.
 16. The speaker assembly ofclaim 15, wherein said driver is free from contact with said seconddiaphragm.
 17. The speaker assembly of claim 14, wherein said firstdiaphragm is an active diaphragm configured to radiate sound energy. 18.The speaker assembly of claim 14, wherein said material rial compositionof said first diaphragm comprises one ply of 120 glass and one ply ofglass Fly Screen layered on separate sides of a Nomax honeycomb core.19. The speaker assembly of claim 14, wherein said first diaphragmcomprises a thickness of about 0.12 inches.
 20. The speaker assembly ofclaim 14, wherein said material composition of said second diaphragmcomprises one ply of 120 glass and one ply of 181 glass layered onseparate sides of a Nomax honeycomb core.
 21. The speaker assembly ofclaim 14, wherein the speaker assembly is installed for use with apublic addressing system of an aircraft.
 22. The speaker assembly ofclaim 14, wherein said gap comprises a dimension of between about 1 and2 inches.
 23. The speaker assembly of claim 14, further comprising acover configured to function operationally with the first diaphragm whensubject to an input signal.
 24. A mobile platform comprising: an audiosystem including: an input device; an amplifier; and a speaker assembly,said speaker assembly including a first diaphragm and a seconddiaphragm; said second diaphragm having a material composition causingit to block sound energy, and reflect said sound energy to said firstdiaphragm.
 25. The mobile platform of claim 24, wherein the mobileplatform is an aircraft.